NASA’s Life changing Arsenic Organism?

NASA held a press conference on December 2, 2010, about their discovery of a bacterium researchers claimed was able to use arsenic, instead of phosphorous, as part of its DNA backbone. This press conference was extremely well advertised and promised the existence of something extraterrestrial. But the organism in question, GFAJ-1, is far from extraterrestrial and can be found on the lakeshores of California. Rather, the findings changed the idea of what science could designate as life. NASA’s original press conference was momentous because of the possibilities it announced for extraterrestrial life – if something on earth can indeed adopt something poisonous as part of its genetic makeup, then life outside of Earth could be wilder than ever imagined. Despite this momentous announcement, critics were unconvinced that the experiment was legitimate, and there still remains controversy over the validity of the experiment’s findings.

Arsenic, normally considered poisonous to any living organism, was shown by Wolfe et al to integrate into the DNA backbone of GFAJ-1, a microorganism that is able to survive under high-arsenic conditions. [1] If factual, the discovery would indicate that life can be formed out of elements other than what has traditionally been known as the building blocks of life – carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Life, as we know it, would forever be redefined.

GFAJ-1 is a strain of the Halomonadaceae bacterium that can be found on the shores of Mono Lake, California. Halomonadaceae is already able to flourish in environments containing arsenic—Mono Lake itself contains a high salt concentration and trace amounts of arsenic.

Scientists gathered GFAJ-1 from the shores of Mono Lake, isolated them, and grew them in a phosphate-low, arsenate-rich medium. They then ran the grown cells through a battery of tests that they claimed showed the integration of arsenic in its backbone. This is the announcement that indicated the possibility of alien life – if something so integral as a phosphorus backbone in DNA could be partially replaced by arsenic, then it is possible for wildly different forms of life to exist in all parts of the universe.

Despite the amazing findings from NASA and Wolfe-Simon et al, some critics saw problems with the study itself. Rosie Redfield listed some problems she viewed on her science blog, RRResearch.

One problem she saw was misinformation. Although the study claims that the modified arsenic-rich cells didn’t grow without arsenic or phosphorous supplements in the medium, the figures show that, in fact, the cells grow threefold without any supplements. Similarly, even though the machine readings of the cell concentrations of the arsenic and phosphate medium were similar, the actual amount of cells differ – there are ten times less cells in the arsenic-rich medium in comparison to the phosphate-rich. [2] The high concentration of cells in medium but low amount of living cells implies that many of the cells in the arsenic medium were dead cells.

Redfield also points out some false information given by the paper about phosphate levels in cells. In the paper, Wolfe-Simon et al claim that cells need 1-3% phosphate to support life. However, this is contradicted by their control: E. coli cells grown in a phosphate-rich medium that contained only 0.5% phosphate. [2]

The controls, too, are under scrutiny. The control organisms were grown in a medium that didn’t have any arsenic, but had added phosphate. This seems likely to skew the controls to having more phosphorous than normal, and doesn’t show a key control: the rate of growth and the intracellular makeup of GFAJ-1 in a medium without arsenic but without added phosphate. This control would be key to showing whether or not the lower amount of phosphorous in GFAJ-1 grown in the arsenic-enriched medium was an effect of the arsenic or of the lower phosphate content. [2]

Perhaps the most important criticism is the doubt that arsenic was actually integrated into the DNA backbone at all. Most of the arsenic in the DNA was found by an extraction and separation process, which took place where there existed small water-soluble molecules not necessarily in DNA or RNA. [3] The high arsenic content in the cells may thus not be proof that the DNA actually contains arsenic, and the entire premise of both the press conference and the paper might be incorrect.

Recently, a paper has been published claiming that scientific precedents show that arsenic integrated into DNA would cause the DNA to disintegrate when in water. [4] This paper could be in response to the Wolfe-Simon team’s initial reluctance to comment on criticisms from blog posts, arguing blogs were an unprofessional medium in which to carry scientific debate.

Wolfe-Simon et al. responded to some of the criticisms in mid-December. They claim that the amount of phosphorus in their medium should have no effect on the GFAJ-1, and that their bacterium and DNA were washed thoroughly before the study. They also emphasized that there is much more research to be conducted on this bacterium before fully answering to whether arsenic can replace phosphorus in DNA for some organisms. [5]

The resulting controversy over the GFAJ-1 organism challenged NASA’s findings and the supremacy of the scientific journal. The initial reports of NASA’s findings were greatly overblown; the GFAJ-1 has not completely integrated arsenic in the DNA backbone. There are parts of the study that are questionable, including its methodology. Many scientists voiced their criticism through their personal blogs, which resulted in the legitimacy of such research blogs being challenged by the scientific community.

Despite the controversy, the study reveals at least the possibility of the existence of organisms with unusual genetic structures that are completely foreign to the ones scientists currently know. It also indicates the feasibility of different evolutionary genetic adaptations that could result in radically different life forms than what people think of today. Ultimately, though the study itself remains contested, the GFAJ-1 study changed the way scientists look at the definition of “life.” NASA wasn’t too far off when they related the findings to alien life; by challenging the notion that all life must contain certain elements in certain structures, the Wolfe-Simon team opens the possibility that life may exist on planets previously thought uninhabitable.

References

  1. Wolfe-Simon F, Blum JS, Kulp TR, Gordon GW, Hoeft SE, Pett-Ridge J, et al.  “A bacterium that can grow by using arsenic instead of phosphorus”. Science [Internet]. 2010 Dec [cited 2010 Dec 2]. Available from: http://www.ironlisa.com/WolfeSimon_etal_Science2010.pdf.
  2. Redfield, Rosie. “Arsenic-Associated Bacteria (NASA’s claims).” RRResearch. 2010 Dec 4. Available from: http://rrresearch.blogspot.com/2010/12/arsenic-associated-bacteria-nasas.html
  3. Hu, Jim. “Ordinary Evidence Would Do.” Blogs for Industry. 2010 Dec [cited 2010 Dec 3]. Available from: http://dimer.tamu.edu/simplog/archive.php?blogid=3&pid=6940
  4. Fekr, Mostafa I.; Tipton, Peter A.; Gates, Kent S. “Kinetic Consequences of Replacing the Internucleotide Phosphorus Atoms in DNA with Arsenic.” ACS Chemical Biology. 2011 Jan [cited 2011 Jan 26]. Available from:  http://pubs.acs.org/doi/abs/10.1021/cb2000023
  5. Redfield, Rosie. “Comments on Dr. Wolfe-Simon’s response.” RRResearch. 2010 Dec [cited 2010 Dec 16] Available from: http://rrresearch.blogspot.com/2010/12/text.html
  6. Apers0n. [photograph] 2009. Available at: http://commons.wikimedia.org/wiki/File:DNA_Double_Helix.png

Annie Kang is a fourth-year English major at the University of Chicago. Please join The Triple Helix Online on Facebook. Follow The Triple Helix Online on Twitter.